<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="https://unpkg.com/vue@next"></script>
</head>

<body>
  <div id="root"></div>
  <script>

    const app = Vue.createApp({
      template: `<div>{{age}}</div>`,
      setup() {
        const { reactive, toRefs ,toRef} = Vue
        const data = reactive({ name: 'dell' })
        const  age  = toRef(data,'age')
        setTimeout(() => {
          age.value = 18;
        }, 2000)
        return { age }
      }
    });

    const vm = app.mount('#root');
  </script>
</body>

</html>